Update README.md

Author: brbartle

Registration/README.md

@@ -1,17 +1,18 @@
 # Registration
 
-This script must be run from the Host machine. As a prerequisite, make sure that you have an Azure subscription and that you have installed Azure PowerShell:
+This script must be run from the Host machine. As a prerequisite, make sure that you have an Azure subscription, that you have installed Azure PowerShell, and that you have registered the AzureStack resource provider:
 
 ```powershell
 Install-Module -Name AzureRM
+Register-AzureRmResourceProvider -ProviderNamespace 'microsoft.azurestack'
 ```
 
 This script helps you to run through the steps of registering your Azure Stack with your Azure subscription. Additional details can be found in the [documentation](https://docs.microsoft.com/en-us/azure/azure-stack/azure-stack-register).
 
 To run the script:
 
 ```powershell
- RegisterWithAzure.ps1 -azureDirectory YourDirectory -azureSubscriptionId YourGUID -azureSubscriptionOwner YourAccountName
+RegisterWithAzure.ps1 -azureCredentials YourCredentialObject -azureAccountId YourAccountName -azureSubscriptionId YourSubscriptionGUID -azureDirectoryTenantName YourAADTenantName
 ```
 
-You will be prompted for your Azure credentials one more time as well as prompted to click "Enter" twice as the script runs.
+AzureCredentials are not mandatory, if you do not pass in an Azure Credential object you will be prompted for your Azure credentials before continuing.